One of the most important characteristics of the third generation mobile communication system is the imbalance of traffics in uplink and downlink. The traffic in the downlink is generally greater than that in the uplink. In regard to such requirement characteristic, the 3GPP (3rd Generation Partnership Project) has introduced High Speed Downlink Packet Access (HSDPA) property into the 3G specifications. In the HSDPA property, a higher downlink packet traffic rate is provided by introducing Adaptive Modulation and Coding (AMC) technique, Hybrid Automatic Retransmission Request (HARQ) technique and relevant techniques for reducing network processing time delay, so as to improve spectrum utilization efficiency.
In the HSDPA technology for a TD-SCDMA system, new physical channels including High Speed Physical Downlink Shared Channel (HS-PDSCH), Shared Control Channel for HS-DSCH (HS-SCCH) and Shared Information Channel for HS-DSCH (HS-SICH) are introduced, and the above physical channel resources in a cell are shared through a resource pool by a number of users in the cell in a time division or code division manner. Wherein, the HS-PDSCH is used to carry service data of the users. Information such as HS-PDSCH code resources, transmission block size and modulation mode, used by each user during different transmission time intervals (TTI), is indicated on the HS-SCCH by a NodeB. And the following information is included in the HS-SCCH:                spread spectrum code set information (8 bits): xccs,1, xccs,2, . . . , xccs,8;        time slot information (5 bits): xts,1, xts,2, . . . , xts,5;        modulation mode information (1 bit): xms,1;        transmission block size information (6 bits): xtbs,1, xtbs,2, . . . , xtbs,6;        hybrid automatic retransmission request process information (3 bits): xhap,1, xhap,2, xhap,3;        redundancy version information (3 bits): xrv,1, xrv,2, xrv,3;        new data indication (1 bit): xnd,1;        cyclic sequence number of the HS-SCCH (3 bits): xhcsn,1, xhcsn,2, xhcsn,3;        identification number of a user equipment (UE) (16 bits): xue,1, xue,2, xue,16.        
Herein:
The modulation mode information is indicated by 1 bit, where 0 represents QPSK and 1 represents 16QAM.
The transmission block size information is indicated by 6 bits which represents an index of a corresponding transmission block in an index table of HSDPA transmission block size corresponding to a capability level to which the user equipment (UE) pertains. The respective index table of transmission block size corresponding to each capability level can be found and the table contains 64 transmission block sizes supported by the UE with the capability level. After the UE receives the information on the HS-SCCH, it will receive succeeding HS-PDSCH information on its designated code channel according to the modulation mode and transmission block size in the received information.
With the development of the technology, it becomes possible to use 64QAM in the HSDPA. However, because the modulation mode information can be indicated by only one bit, only two modulation modes can be represented such that 64QAM is unable to be represented according to the current structure. If the frame structure of the HS-SCCH is changed, a compatibility problem will be caused. Therefore, how the UE can use a planned modulation mode for the dynamic transmission block size to represent the 64QAM without changing the frame structure of the HS-SCCH on a premise that the compatibility is ensured has become a problem urgent to be solved.